In many different applications, gas from a gas storage, typically under high pressure, is successively used for a particular purpose at an end equipment. The purpose can e.g. be a chemical reaction, for combustion or for use as a transport medium. A more specific application can be found in space technology, where the mass of streaming gas is utilized in a gas thruster for propelling e.g. a space vehicle.
In arrangements of this kind, it is often vital that the final application is not exposed for gas of a too high pressure. Typically, a pressure regulator is provided at the exit of the gas storage to insure that the pressure at the end equipment is sufficiently low. However, if such a pressure regulator fails, gas of a high pressure may be released and the end equipment may thus be damaged. Also other equipment situated in the vicinity of the end equipment may be damaged as well. In cases the end equipment is difficult to repair or exchange, e.g. due to hazardous environments or simply being sent away on a space mission, such failure may cost huge amount of money.
These problems can be met by connecting different kinds of monitoring and/or safety valve devices to the supply line between the pressure regulator of the gas storage and the end equipment. If the pressure in the supply line becomes too high, gas is allowed to escape from the supply line in a manner not harming the end equipment. Different types of arrangements have different advantages and disadvantages. For instance, a passive safety valve is often relatively simple, however, it is often difficult to define a very exact release pressure. An active safety valve on the other hand, being operated in dependence e.g. on a monitored gas pressure can be provided with “intelligence” for not opening unnecessarily. However, such equipment relies on the error-free operation of the gas pressure monitor. Furthermore, pure safety valves are not suitable for handling temporary failures, since they typically are not re-sealable.
A common problem with all kinds of prior art safety valve arrangements is that they typically introduce new equipment which can fail as such, and which increases the complexity of connections. An arrangement of the type described above is typically requested to be extremely well sealed off when not being in use. Each connection of a new piece of equipment to a supply line increases the risks for leaks to be introduced in the system. Furthermore, each additional component typically also adds to the weight and volume, which can be a great disadvantage, at least for space applications.